U.S. patent application number 13/397015 was filed with the patent office on 2012-06-14 for non-isocyanate-based polyurethane and hybrid polyurethane-epoxy nanocomposite polymer compositions.
This patent application is currently assigned to Huntsman Advanced Materials Americas LLC. Invention is credited to Constantinos D. Diakoumakos, Dimiter Lubomirov Kotzev.
Application Number | 20120149842 13/397015 |
Document ID | / |
Family ID | 33560891 |
Filed Date | 2012-06-14 |
United States Patent
Application |
20120149842 |
Kind Code |
A1 |
Diakoumakos; Constantinos D. ;
et al. |
June 14, 2012 |
Non-Isocyanate-Based Polyurethane and Hybrid Polyurethane-Epoxy
Nanocomposite Polymer Compositions
Abstract
A fast curable non-isocyanate-based polyurethane- and
polyurethane-epoxy network nanocomposite polymeric compositions are
derived upon crosslinking a mixture comprising of natural or
modified nano-clay [ionic phyllosilicate] with platelet thickness
in the scale of .ANG. (.about.1 nm) and aspect ratio
(length/thickness) higher than 10 (nm)] preferably natural or
modified montmorillonite with either a monomer(s) or oligomer(s)
bearing at least one cyclocarbonate group or a mixture of the
latter with an epoxy resin, with a hardener, which is a monomer or
oligomer or mixtures therefrom, bearing primary and/or secondary
amino groups. The use of the nanoclays reduces the gel time and
increases the adhesion of the cured polyurethane and
polyurethane/epoxy hybrid and also reduces its water
absorption.
Inventors: |
Diakoumakos; Constantinos D.;
(Cambridge, GB) ; Kotzev; Dimiter Lubomirov;
(Corby, GB) |
Assignee: |
Huntsman Advanced Materials
Americas LLC
The Woodlands
TX
|
Family ID: |
33560891 |
Appl. No.: |
13/397015 |
Filed: |
February 15, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10567945 |
Feb 10, 2006 |
8143346 |
|
|
PCT/EP2004/051796 |
Aug 13, 2004 |
|
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13397015 |
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Current U.S.
Class: |
524/859 ; 528/55;
977/773 |
Current CPC
Class: |
C08G 71/04 20130101 |
Class at
Publication: |
524/859 ; 528/55;
977/773 |
International
Class: |
C08L 75/04 20060101
C08L075/04; C08G 71/04 20060101 C08G071/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 13, 2003 |
EP |
03255011.3 |
Claims
1. A non-isocyanate based polyurethane obtained from the reaction
of: (a) one or more polymerisable organic materials having at least
one cyclocarbonate group; (b) at least one nano-clay having a
platelet thickness of less than 25 .ANG. and an aspect ratio higher
than 10 or a nanocomposite formed from the nano-clay; (c) at least
one hardener; and optionally (d) a compound containing one or more
epoxy groups.
2. The non-isocyanate based polyurethane of claim 1 wherein
component (a) is a compound of formula I: ##STR00002## wherein
R.sub.1 and R.sub.2 are each independently hydrogen, or a linear or
branched, or cyclic, saturated or unsaturated group optionally
substituted with one or more heteroatoms, oxygen-containing groups
or nitrogen-containing groups.
3. The non-isocyanate based polyurethane of claim 1 wherein
component (b) is present in an amount of from 0.1 to 95% w/w based
on the total weight of the composition.
4. The non-isocyanate based polyurethane of claim 1 wherein
component (b) is present in an amount of from 4 to 20% w/w based on
the total weight of the composition.
5. The non-isocyanate based polyurethane of claim 1 wherein the
nano-clay has aspect ratio higher than 50.
6. The non-isocyanate based polyurethane of claim 1 wherein the
thickness of the nano-clay platelets is less than 10 .ANG..
7. The non-isocyanate based polyurethane of claim 1 wherein the
nano-clay is a natural or modified bentonite, saponite, hectorite,
montmorillonite or synthetic mica fluoride.
8. The non-isocyanate based polyurethane of claim 1 wherein the
nano-clay is a natural or modified montmorillonite.
9. The non-isocyanate based polyurethane of claim 1 additionally
containing one or more reinforcement fibres and/or one or more
toughening agents.
10. The non-isocyanate based polyurethane of claim 1 additionally
containing one or more fillers and/or one or more pigments.
11. The non-isocyanate based polyurethane of claim 1 additionally
containing one or more drying agents, and/or one or more
stabilizers, and/or one or more surface tension modifiers.
12. The non-isocyanate based polyurethane of claim 1 additionally
containing a solvent or a solvent mixture.
13. The non-isocyanate based polyurethane of claim 1 additionally
containing a diluent or a diluent mixture.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/567,945, currently pending, which is the
National Phase of International Application PCT/EP2004/051796 filed
Aug. 13, 2004 which designated the U.S. and which claims priority
to European (EP) Pat. App. No. 03255011.3 filed Aug. 13, 2003. The
noted applications are incorporated herein by reference
TECHNICAL FIELD
[0002] The present invention relates to polyurethane and
polyurethane/epoxy compositions and to methods of their
manufacture.
BACKGROUND ART
[0003] Processes and materials that are, or are suspected to be,
ecologically damaging are increasingly unacceptable and alternative
ecologically safer solutions are demanded. Conventionally,
polyurethanes are manufactured by the reaction of organic materials
containing two or more hydroxyl groups with other organic materials
(monomers, dimers, trimers and oligomers) containing two or more
isocyanate groups. Such isocyanates are highly toxic and are
produced from by an even more toxic starting material, phosgene.
Secondly, polyurethane production is prone to an undesirable
side-reaction between the isocyanate groups and moisture, which
yields carbon dioxide within the polyurethane mass, resulting in
bubbles of carbon dioxide being trapped in the finished material,
causing the polyurethane to be porous. Conventional polyurethanes
are unstable in the presence of water and have a poor chemical
resistance to aqueous solutions of acids and alkalis, which limits
their use.
[0004] A series of relatively recent patents disclose polyurethane
or polyurethane-epoxy hybrid compositions based on the reaction
between, on the one hand, oligomer(s) bearing cyclocarbonate groups
or both epoxy groups and cyclocarbonate groups and, on the other
hand, amines. More particularly, U.S. Pat. No. 5,340,889 discloses
a method for producing linear non-isocyanate polyurethanes from the
reaction of cyclocarbonate derivatives and amines.
[0005] SU-1,754,748 deals with an epoxy-based composite material
for flooring applications that includes an oligomeric
cyclocarbonate modifier with a monofunctional hardener
(aminophenol) for the modifier, resulting in an epoxy-based
material with immobilized non-isocyanate oligo-urethane
moieties.
[0006] U.S. Pat. No. 5,175,231 and U.S. Pat. No. 6,495,637 disclose
a multi-step process for the preparation of a network comprising
non-isocyanate polyurethane links for use as a hardener for epoxy
resins.
[0007] U.S. Pat. No. 4,785,615 discloses polymer compositions
containing urethane groups that are capable of being crosslinked by
crosslinking agents, prepared without the use of isocyanates by
reacting polyamino compounds with polycarbonates and if
appropriate, reacting the product further with polycarboxylic acids
to form a series of products intended for use as adhesives and
paints, especially aqueous baking paint formulations and aqueous
curable paints that can be deposited by anaphoresis.
[0008] U.S. Pat. No. 6,120,905 discloses hybrid non-isocyanate
network polyurethanes formed by crosslinking at least one
cyclocarbonate oligomer with an average functionality of from about
2.0 to about 5.44 and at least one of these cyclocarbonate
oligomers consists from about 4 to about 12% w/w of terminal epoxy
groups, with one amine oligomer. The patent also relates to methods
of making hybrid non-isocyanate polyurethane networks for use in
composite materials containing a fibre reinforcement (glass fibre,
carbon fibre, basalt fibre and mixtures thereof), or a particulate
reinforcement, e.g. a metal oxide or a metal aluminate salt.
[0009] EP-1,020,457 and U.S. Pat. No. 6,407,198 relate to the
synthesis of polyfunctional polycyclocarbonate oligomers. The
polycyclocarbonates are prepared by the reaction of
oligocyclocarbonates containing terminal epoxy groups with primary
aromatic diamines and they were used for the preparation of hybrid
materials for adhesives, sealants, composite materials, coatings or
synthetic leather. It is mentioned that pigments and fillers (e.g.
barium sulphate, titanium dioxide, silica, aluminate cement and
ferrous oxides pigments) can be also added in the preparation of
adhesives compositions
[0010] EP-1,070,733 relates to the synthesis of polyaminofunctional
hydroxyurethane oligomers and hybrids prepared therefrom. It states
that it is impossible to form composite polyurethane/epoxy resins
by curing a composition containing both epoxy groups and
cyclocarbonate groups with a hardener containing primary amine
groups because of the competition between the epoxy and
cyclocarbonate groups for reaction with the primary amines. It
therefore proposes a curable composition containing an oligomer
containing both a cyclocarbonate ring and an epoxy ring.
[0011] Micheev V. V. et al. report (Lakokrasochnye Materialy I Ikh
Primenenie, 1985, 6, 27-30) that co-curing of oligomeric
cyclocarbonate resins and epoxies with polyamines yields products
with enhanced properties over monolithic non-isocyanate-based
polyurethanes but they do not include any comparative example in
their study.
[0012] In 1990, researchers at TOYOTA Central Research &
Development Laboratories (Japan) [a] Fukushima, Y. et all., J.
Inclusion Phenom., 1987, 5, 473, b] Fukushima, Y, et all., Clay
Miner., 1988, 23, 27, c] Usuki, A. et all., J. Mater. Res., 1993,
8, 1174, d] Yano K. et all., J. Polym. Sci. Part A: Polymer Chem.,
1993, 31, 2493, e) Kojima, Y. et all., J. Polym. Sci. Part A:
Polymer Chem., 1993, 31, 983] disclosed the enhancement in
mechanical properties of nylon-clay nanocomposites.
[0013] Researchers have concentrated on four nanoclays as potential
nanoscale particles: a) hydrotalcite, b) octasilicate, c) mica
fluoride and d) montmorillonite. The first two have limitations
both from a physical and a cost standpoint. The last two are used
in commercial nanocomposites. Mica fluoride is a synthetic
silicate, montmorillonite (MMT) is a natural one. The theoretical
formula for montmorillonite is:
M.sup.+.sub.y(Al.sub.2-yMg.sub.y)(Si.sub.4)O.sub.10(OH).sub.2*nH.sub.2O
[0014] Ionic phyllosilicates have a sheet structure. At the
Angstrom scale, they form platelets, which are 0.7-1 nm thick and
several hundred nanometers (about 100-1000 nm) long and wide. As a
result, individual sheets have aspect ratios (Length/Thickness,
L/T) varying from 200-1000 or even higher and, after purification,
the majority of the platelets have aspect ratios in the 200-400
range. In other words, these sheets usually measure approximately
200.times.1 nm (L.times.T). These platelets are stacked into
primary particles and these primary particles are stacked together
to form aggregates (usually about 10-30 .mu.m in size). The
silicate layers form stacks with a gap in between them called the
"interlayer" or "gallery". Isomorphic substitution within the
layers (Mg.sup.2+ replaces Al.sup.3+) generates negative charges
that are counterbalanced by alkali or alkaline earth cations
situated in the interlayer. Such clays are not necessarily
compatible with polymers since, due to their small size, surface
interactions such as hydrogen bonding become magnified. Thus, the
ability to disperse the clays within some resins is limited and at
the beginning, only hydrophilic polymers (e.g. PVA) were compatible
with the clays because silicate clays are naturally hydrophilic.
But, it was found that the inorganic cations situated in the
interlayer can be substituted by other cations. Cationic exchange
with large cationic surfactants such as alkyl ammonium-ions,
increases the spacing between the layers and reduces the surface
energy of the filler. Therefore, these modified clays (organoclays)
are more compatible with polymers and form polymer-layered silicate
nanocomposites. Various companies (e.g. Southern Clays (of 1212
Church Street, Gonzales, Tex. USA 8629), Sud Chemie, Nanocor, etc.)
provide a whole series of both modified and natural nano clays,
which are montmorillonites. Apart from montmorillonites, hectorites
and saponites are the most commonly used layered silicates.
[0015] A nanocomposite is a dispersion, often a near-molecular
blend, of resin molecules and nanoscale particles. Nanocomposites
can be formed in one of the following three ways: a) melt blending
synthesis, b) solvent based synthesis and c) in-situ
polymerization, as is known in the art.
[0016] There are three structurally different types of
nanocomposites: 1) intercalated (individual monomers and polymers
are sandwiched between silicate layers) 2) exfoliated (a "sea" of
polymer with "rafts" of silicate), and 3) end-tethered (a whole
silicate or a single layer of a silicate is attached to the end of
a polymer chain).
[0017] Glass transition temperature is a fundamentally important
property of polymers since it is the temperature at which
properties of the polymer change radically. In some instances, it
is desirable to have a high glass transition temperature for a
polyurethane polymer.
[0018] Gel time is also an important production parameter and fast
gel times allow a polymer to be manufactured or formed more
rapidly. Gel times and cure times are obviously related and both
will be referred to in the present specification. In addition, fast
cure times allow adhesives to set quickly to produce the desired
bond.
DISCLOSURE OF THE INVENTION
[0019] The present invention provides a composition for forming a
non-isocyanate-based polyurethane- and polyurethane-epoxy network
nanocomposite polymeric composition, comprising the following
components: [0020] (a) a polymerisable organic material that bears
at least one cyclocarbonate group or a mixture thereof; [0021] (b)
a natural or synthetic, modified or unmodified nano-clay [ionic
phyllosilicate] with a platelet thickness of less than 25 .ANG.
(.about.2.5 nm), more preferable less than 10 .ANG. (.about.1 nm),
and most preferably between 4-8 .ANG. (.about.0.5-0.8 nm) and an
aspect ratio (length/thickness) higher than 10, more preferably
higher than 50 and most preferably higher than 100 or a mixture
thereof or a nanocomposite formed from such a nano-clay or
nano-clay mixture; preferably the nano-clay is a natural or
modified montmorillonite; and [0022] (c) at least one hardener for
component (a), which preferably is a primary and/or secondary amine
or a mixture thereof.
[0023] The composition optionally also includes, as a further
component (d), a compound containing one or more epoxy group.
[0024] Component (a) can be monomer or a dimer or oligomer, i.e.
any compound that can be polymerised with itself or with another
molecule to form a chain or network containing of monomer
units.
[0025] As used herein the term "nanoclay" means a natural or
synthetic, modified or unmodified ionic phyllosilicate with a
platelet structure, the platelets being separable from each other
on incorporation into the above composition and having a thickness
of less than 25 .ANG. (.about.2.5 nm), more preferable less than 10
.ANG. (.about.1 nm), and most preferably between 4-8 .ANG.
(.about.0.5-0.8 nm) and an aspect ratio (length/thickness) higher
than 10:1. A nanocomposite is a blend of resin molecules and a
nano-clay, as discussed above. A modified nanoclay is a natural
nanoclay that has been subject to a cation exchange reaction of the
intergallery cations.
[0026] The incorporation of the nanoclays and nanocomposites has,
as is evident from the discussions below, a beneficial effect on
the speed of gelling and cure time even if the platelets are not
separated and so the present invention is not limited to the
platelets being separated and dispersed through the composition.
However, it is preferred that the platelets separated and dispersed
since that provides beneficial improvement in the physical
properties such as water uptake and strength as well as improved
gel time. The preferred methods for dispersion of the nano-clay is
sonification or high-shear mixing. The present invention can use
all of types 1 to 3 of nanocomposites discussed above.
[0027] Component (a) is preferably a compound of the general
formula:
##STR00001##
where R.sub.1 and R.sub.2 can each independently be hydrogen, or a
linear, branched, cyclic (aromatic/heteroaromatic/cycloaliphatic),
saturated or unsaturated (e.g. vinyl, (meth)acrylate moieties,
etc.) group and can also contain heteroatoms (e.g. silicon) or more
preferably oxygen-containing groups (e.g. terminal or linking
further 1,3-dioxolan-2-one rings, epoxy rings, or ester, ether,
carboxyl groups, or hydroxy) and/or nitrogen (e.g. terminal or
linking amino, imino, tertiary coordinated nitrogen).
[0028] The polymerisable cyclocarbonate-containing organic material
may be prepared by reacting an organic material containing an epoxy
group via a cyclocarbonation reaction with carbon dioxide and a
catalyst, e.g. tetraethylammonium bromide. Preferred
cyclocarbonates are those presented in FIG. 6 and which may also
include different percentages of cyclocarbonate groups. However the
cyclocarbonate component (a) may be any molecule that can be
derived from an epoxy-containing compound that has been subject to
cyclocarbonation, e.g. an epoxy resin component (d) discussed
below. Indeed, component (d) may be residual epoxy resin remaining
form partial cyclocarbonation of an epoxy resin to form component
(a).
[0029] Resins presenting both cyclocarbonate and epoxy
functionalities are useful in the present invention; they are known
in the art and are described for example in U.S. Pat. No. 5,175,231
and EP1070733. Such mixed functionality resins may be formed by the
incomplete cyclocarbonation of a polyepoxy resin, i.e. some but not
all the epoxide rings are reacted with carbon dioxide to form
cyclocarbonate rings.
[0030] Cyclocarbonate resins are widely known in the art; see for
example U.S. Pat. No. 5,175,231, U.S. Pat. No. 6,495,637, U.S. Pat.
Nos. 5,340,889, 6,120,905, U.S. Pat. No. 4,699,974, U.S. Pat. No.
3,072,613, U.S. Pat. No. 6,407,198 U.S. Pat. No. 4,758,615, U.S.
Pat. No. 6,120,905, EP-1020457 and EP1070733 and any of the
cyclocarbonates described therein can be used in the present
invention.
[0031] The hardener (reactant (c)) may be any chemical materials
known in the art for curing cyclocarbonate resin component (a) and,
when present, epoxy component (d). Such materials are sometimes
referred to as curatives, curing agents or activators and are
incorporated into the thermoset polymeric network formed by
condensation, chain-extension and/or crosslinking of the
cyclocarbonate and, when present, epoxy resins. Catalysts and/or
accelerators can also be added to promote curing by catalytic
action. Preferably the hardener contains two or more primary or
secondary amine groups, although primary amines are preferred. Thus
they may be, for example, aliphatic, aromatic, cycloaliphatic di-
or poly-amines. The hardener may be a polyaminofunctional
hydroxyurethane oligomer, i.e. an amino-terminated adduct resulting
from the reaction of a molecule containing a cyclocarbonate or
epoxy group with a polyamine. Preferably, the amine groups in the
hardener are not directly connected to an aromatic ring.
[0032] The hardener may be an amine terminated amine-epoxy adduct,
that is to say an adduct between one or more molecules containing
an epoxy ring and one or more compounds containing two or more
amine groups such that there is a stoichiometric excess of amine
groups so that the amine groups are available for curing component
(a) and/or (d). Carboxylic acid anhydrides, carboxylic acids,
phenolic novolac resins, thiols (mercaptans), water, metal salts
and the like may also be utilized as additional reactants in the
preparation of the amine-epoxy adduct or to further modify the
adduct once the amine and epoxy have been reacted.
[0033] Amine epoxy adducts forming component (a) or (c) are well
known in the art, see e.g. U.S. Pat. Nos. 3,756,984, 4,066,625,
4,268,656, 4,360,649, 4,542,202, 4,546,155, 5,134,239, 5,407,978,
5,543,486, 5,548,058, 5,430,112, 5,464,910, 5,439,977, 5,717,011,
5,733,954, 5,789,498, 5,798,399 and 5,801,218, each of which is
incorporated herein by reference in its entirety.
[0034] The composition optionally also includes a further component
(d) in the form of a compound containing one or more epoxy group.
Instead of providing a separate epoxy component (d), an epoxy group
may be included in component (a) (the organic material containing
the cyclocarbonate group). A hardener for the epoxy groups should
also be provided in the composition, the epoxy hardener is
preferably the same as the hardener for the cyclocarbonate
component (a), i.e. component (c) or may be any other known
hardener for an epoxy system.
[0035] The epoxy resin may be any thermosettable resin having an
average of more than one (preferably, about two or more) epoxy
groups per molecule. Epoxy resins are well-known in the art and are
described, for example, in the chapter entitled "Epoxy Resins" in
the Second Edition of the Encyclopedia of Polymer Science and
Engineering, Volume 6, pp. 322-382 (1986). Suitable epoxy resins
include polyglycidyl ethers obtained by reacting polyhydric phenols
such as bisphenol A, bisphenol F, bisphenol AD, catechol, or
resorcinol, or polyhydric aliphatic alcohols such as glycerin,
sorbitol, pentaerythritol, trimethylol propane and polyalkylene
glycols with haloepoxides such as epichlorohydrin; glycidylether
esters obtained by reacting hydroxycarboxylic acids such as
p-hydroxybenzoic acid or beta-hydroxy naphthoic acid with
epichlorohydrin or the like; polyglycidyl esters obtained by
reacting polycarboxylic acids such as phthalic acid,
tetrahydrophthalic acid or terephthalic acid with epichlorohydrin
or the like; epoxidated phenolic-novolac resins (sometimes also
referred to as polyglycidyl ethers of phenolic novolac compounds);
epoxidated polyolefins; glycidylated aminoalcohol compounds and
aminophenol compounds, hydantoin diepoxides and urethane-modified
epoxy resins.
[0036] Component (d) may be an epoxy-terminated amine-epoxy adduct,
that is to say an adduct between one or more molecules containing
at least two epoxy rings and one or more compounds containing at
least one amine groups such that there is a stoichiometric excess
of the epoxy rings so that they are available for forming component
(d). Carboxylic acid anhydrides, carboxylic acids, phenolic novolac
resins, thiols (mercaptans), water, metal salts and the like may
also be utilized as additional reactants in the preparation of the
amine-epoxy adduct or to further modify the adduct once the amine
and epoxy have been reacted.
[0037] Specific examples of suitable commercially available epoxy
resins are those sold under the trade mark ARALDITE such as the
MY-series (e.g. MY-0500, MY-0510, MY-0501, MY-720, MY-740, MY-750,
MY-757, MY-790, MY-791, etc.), the GY-series (e.g. GY-240, GY-250,
GY-260, GY-261, GY-282, etc.) (HUNTSMAN (PREVIOUSLY VANTICO A.G.,
Switzerland), DER-324, DER-332, DEN-431, DER-732 (DOW Chemical Co.,
USA), EPON 813, EPON 8021, EPON 8091, EPON 825, EPON 828, Eponex
1510, Eponex 1511 (SHELL Chemical Co. USA), PEP 6180, PEP 6769, PEP
6760 (Pacific Epoxy Polymers Inc. USA), NPEF-165 (Nan Ya Plastic
Corporation, Republic of China), Ricopoxy 30, Ricotuff 1000-A,
Ricotuff-1100-A, Ricotuff-1110-A (Ricon Resins Inc., USA), Setalux
AA-8502, Setalux 8503 (AKZO Nobel, Netherlands), to mention just a
few.
[0038] The amount of hardener (component (c)) should be at least
the stoichiometric amount required to react with the cyclocarbonate
component (a) and epoxy component (d).
[0039] The composition may also include one or more of the
following: [0040] reinforcement fibres, e.g. glass-, carbon- or
basalt fibres and mixtures thereof; [0041] toughening agents e.g.
carboxy- or amino-terminated butadiene-nitrile rubber, ABS and MBS
core-shell particles or copolymers, silicone rubbers, silicone
core-shell particles; [0042] further fillers with a larger particle
and/or reinforcing agents and/or pigments e.g. metal oxides, metal
hydrates, metal hydroxides, metal aluminates, metal
carbonates/sulphates, starches, talcs, kaolins, molecular sieves,
fumed silica, organic pigments, etc.); [0043] diluents; [0044]
solvents; [0045] thickeners and flow modifiers, e.g. thixotropic
agents; and [0046] other additives commonly used in adhesives,
sealants, paints/coatings, casting resins, cables, in shapable
moulding materials and in finished mouldings or in composite
materials.
[0047] The fillers (which includes substances capable of
functioning as thixotropic or rheological control agents) that may
optionally be present in the composition include any of the
conventional inorganic or organic fillers known in the
thermosettable resin art, including, for example, fibers other than
glass fibers (e.g. wollastinite fibers, carbon fibers, ceramic
fibers, aramid fibers), silica (including fumed or pyrogenic
silica, which may also function as a thixotropic or rheological
control agent), calcium carbonate (including coated and/or
precipitated calcium carbonate, which may also act as a thixotropic
or rheological control agent, especially when it is in the form of
fine particles), alumina, clays, sand, metals (e.g., aluminum
powder), microspheres other than glass microspheres (including
thermoplastic resin, ceramic and carbon microspheres, which may be
solid or hollow, expanded or expandable), and any of the other
organic or inorganic fillers known in the epoxy resin field. The
quantity of thixotropic agent(s) is desirably adjusted so as to
provide a dough which does not exhibit any tendency to flow at room
temperature.
[0048] Other optional components include diluents (reactive or
non-reactive) such as glycidyl ethers, glycidyl esters, acrylics,
solvents, and plasticizers, toughening agents and flexibilizers
(e.g., aliphatic diepoxides, polyaminoamides, liquid polysulfide
polymers, rubbers including liquid nitrile rubbers such as
butadiene-acrylonitrile copolymers, which may be functionalized
with carboxyl groups, amine groups or the like), adhesion promoters
(also known as wetting or coupling agents; e.g., silanes,
titanates, zirconates), colorants (e.g., dyes and pigments such as
carbon black), stabilizers (e.g., antioxidants, UV stabilizers),
and the like.
[0049] The present invention avoids environmentally damaging
isocyanates and provides a cured product with beneficial
physicochemical and mechanical properties, especially the avoidance
of occluded gas bubbles that presently restricts the use of
polyurethane-based materials.
[0050] The polyurethanes and polyurethane-epoxy hybrid materials
containing nano-clays present superior physical and mechanical
properties over their counterparts containing no nano-clays,
particularly improved adhesive properties and reduced water
absorption.
[0051] In addition, the introduction and dispersion in the
nanoscale of modified nano-clays into non-isocyanate-based
polyurethane and hybrid reaction mixtures with epoxy-containing
were found unexpectedly to provide a significant catalytic effect
in the crosslinking reaction between cyclocarbonate groups and the
epoxy groups of components (a) and (d) with the amine groups of the
hardener (c), resulting to significantly faster curing processes
and substantially lower gel times. More particularly a study based
on the gel times of various formulations of the type mentioned
herein, revealed the potential of organoclays and/or mixtures of
organoclays with cyclocarbonated resins as effective accelerators
for the polyepoxy reaction. For example, a significant decrease in
the gel time of a conventional system containing commercially
available epoxide resin, MY-0510, and triethylene pentamine (TEPA)
was recorded when the epoxide also included a highly reactive
cyclocarbonated resin and a properly exfoliated organoclay and the
resulting mixture was crosslinked with TEPA. The present invention
also gives rise to a reduced gel time and also, in some instances a
higher glass transition temperature.
[0052] Furthermore, the incorporation of nano-clays according to
the present invention permits the preparation of
non-isocyanate-based hybrid polyurethane-epoxy linear or network
materials of enhanced physicochemical and mechanical properties by
mixing compounds bearing cyclocarbonate groups with epoxy resins
and subsequently crosslinking the mixture with amine(s).
EP-A-1,070,733 states that it is impossible to prepare a
non-isocyanate polyurethane-epoxy hybrid materials containing both
epoxy and cyclocarbonate groups but we have not found this
problematic when using nano-clays in the composition.
[0053] According to a further aspect of the present investigation,
the polymeric compositions related to this invention can also
include a solvent.
[0054] The compositions of the present invention can be made
non-flammable by introducing flame-retardants.
[0055] The newly developed non-isocyanate-based polyurethane- and
hybrid polyurethane-epoxy nanocomposites described in the present
invention are especially useful in applications as adhesives,
sealants, paints/coatings, casting resins, reinforcing or
thixotropic agents, cables, in shapable moulding materials and in
finished mouldings or composite materials.
[0056] In addition to the above-mentioned catalytic effect and the
increased curing speeds and decreased gel times, the main
advantages of introducing layered silicates into a conventional
polymeric composition can be summarized as follows: a) they have a
low cost, b) low loading levels (typically up to 10%) of layered
silicates are typically required, c) safe handling due to the use
of non-toxic raw materials d) they do not damage the environment,
e) they are light weight, f) they provide materials of high modulus
of elasticity and strength g) they decrease the moisture, solvent
and gas permeability h) the silicates are transparent and therefore
do not affect the appearance of the polymer, i) they provide
flexibility, m) they provide enhanced flame retardancy.
BRIEF DESCRIPTION OF THE DRAWINGS/SCHEMES
[0057] The attached Figures are referred to in which:
[0058] FIG. 1 is a FT-IR spectra of L-803, RPU-1 and NPU-1;
[0059] FIG. 2 is a FT-IR spectra of RPU-4 and NPU-4 (compositions
RPU-4 and NPU-4 are essentially the same to RPU-1 and NPU-1
respectively (the FT-IR of which are presented in FIG. 1), but
correspond to different curing time (4 days at ambient
temperature);
[0060] FIG. 3 is a graph showing the isothermal water uptake of two
compositions (RPU and NPU).
[0061] FIG. 4 is a graph showing the isothermal water uptake of two
compositions after they have been cured for 1 hour (RPUH1 and
NPUH1);
[0062] FIG. 5 is a graph showing the isothermal water uptake of the
two compositions of FIG. 4 but after they have been cured for 2
hours (RPUH-2 and NPUH2.
[0063] FIG. 6 Chemical structures of epoxy resin MY-0510
(represented as a monomer) and cyclocarbonate resins MY-0500CC
(represented as a monomer) and L-803.
EXAMPLES
Raw Materials
[0064] The raw materials and their suppliers that were used in the
Examples are set out in Table 1.
TABLE-US-00001 TABLE 1 Material Description Supplier Cloisite
Na.sup.+ A natural nano-clay (Montmorillonite) Southern Clays
Cloisite 25A A nanoclay (montmorillonite) treated Southern
(d.sub.001 = with a surface modifier (dimethyl, Clays 18.6 .ANG.)
hydrogenated tallow, 2-ethylhexyl quaternary ammonium with a:
methyl sulfate anion) Nanofil 32 A nano-clay treated with a surface
Sud (d.sub.001 = modifier (stearylbenzyldimethyl- Chemie 18.0
.ANG.), ammonium salt) Montmorillonite Nano-clay Aldrich K10
Chemical Company MY-0510 epoxy resin (see FIG. 1), MW = Huntsman
303, functionality = 3; (previously Vantico Ltd) MY-0500CC
cyclocarbonate resin (see FIG. 1), Chemonol MW = 462, functionality
= 3 Ltd Laprolate cyclocarbonate resin (see FIG. 1), Chemonol
803(L-803) MW = 957, functionality = 3, Ltd triethylene An amine;
MW = 189, functionality: Aldrich pentamine 7 towards epoxy resins
and 2 towards Chemical (TEPA) cyclocarbonate resins Company
diethylene An amine; MW = 103, functionality: Aldrich triamine 5
towards epoxy resins and 2 towards Chemical (DETA) cyclocarbonate
resins Company Ethacure-100 diethyltoluene diamine, MW = 178, Ethyl
functionality: 4 towards epoxy resins Chemicals and 2 towards
cyclocarbonate resins Group Arquad- mixture of (a) 70-80% benzyl
Akzo Nobel- DMHTB-75 hydrogenated tallow chloride, (b) Rockwood
1-4% alkyl trimethyl hydrogenated Additives tallow chloride, (c)
10-20% Isopropanol and (d) 5-10% water Benzyl Fluka trimethyl
ammonium chloride
Test Methods
[0065] Gel time measurements were carried out at 36.degree. C. on a
Micheler apparatus equipped with a digital temperature controller
(acc.: .+-.0.1.degree. C.).
[0066] Glass transition temperatures (LI A differential scanning
calorimeter (DSC), DSC-2920 (TA Instruments) equipped with a high
temperature cell was used to determine glass transition
temperatures (T.sub.g) (nitrogen atmosphere, heating rate:
10.degree. C./min). Some glass transition temperatures were
measured using dynamic mechanical analysis (DMA).
[0067] Dynamic mechanical analyses (DMA) A Rheometrics Dynamic
Analyser RDA-700 with torsional rectangular fittings (specimens: 55
mm in length, 10 mm in width and 2 mm in thickness) was used for
dynamic mechanical analyses (strain: .+-.1%, frequency 1 Hz).
[0068] Lap shear measurements at 25.degree. C., were performed on
an Instron 4467 (crosshead speed of 10 mm/min, substrates:
aluminium cleaned only with acetone) according to ISO 4587.
[0069] Isothermal water uptake measurements were carried out at
20.degree. C. (acc.: .+-.2.degree. C.) and relative humidity 73%
(acc.: .+-.2%). The samples were cured at room temperature
(25.degree. C.) for 1 day in a desiccator and then post-cured and
dried at 60.degree. C. for 2 days.
Example 1
Preparation of a mixture of a cyclocarbonate resin with an epoxy
resin
[0070] 80 g of MY-0510 and 20 g of MY-0500CC were placed in a round
bottom flask equipped with a mechanical stirrer, heating mantle and
a digital temperature controller (acc. .+-.1.degree. C.). The
mixture was heated at 60.degree. C. for 3 h under high shear
(3000-3500 rpm). The solution was then removed from the flask and
kept in a glass container. The solution was assigned the name:
MY-20CC-80EP
Examples 2-7
Preparation of dispersions of nano-clays into various polymers
[0071] Solventless dispersions of Cloisite 25A (Southern Clays) and
Nanofil32 Chemie), into various resins or polymerizable monomers
were carried out via the following general procedure:
[0072] 100 parts by weight of a resin or a resin mixture, as set
out in see Table 2, was mixed with one of the aforementioned
nano-clays (10 parts by weight) and placed in a round bottom flask
equipped with a mechanical stirrer, heating mantle and a digital
temperature controller (acc. .+-.1.degree. C.). The mixture was
heated at a temperature between 50 to 60.degree. C. for 6 h under
high shear (3-3500 rpm). The dispersed product was then removed
from the flask and placed in a plastic container. Table 2,
summarises the preparation of each of the dispersions (resin,
nano-clay, temperature) and the product names assigned to them.
TABLE-US-00002 TABLE 2 Resin or Mixture Temperature Product Example
of Resins Nano-clay (.degree. C.) name 2 L-803 Cloisite 25A 60
D4408 3 L-803 Nanofil 32 60 D3808 4 MY-20CC- Cloisite 25A 60 D4508
80EP* 5 MY-20CC- Nanofil 32 60 D3708 80EP* 6 MY-0510 Cloisite 25A
60 D4208 7 MY-0510 Nanofil 32 60 D3508 *See Example 1
Examples 8-15
Preparation of Mixtures of Nano-Clays into Various Polymers
[0073] Solventless dispersions of Cloisite 25A, Cloisite Na
(Southern Clays), Nanofil32 Chemie), and Montmorillonite K10 in
MY-0510 epoxy resin or MY-20CC-80EP were formed via the following
general procedure:
[0074] 100 parts by weight of MY-0510 resin or the resin mixture
MY-20CC-80EP was hand-mixed for 5-10 min with a nano-clay (10 parts
by weight) at ambient temperature, as detailed in Table 3.
TABLE-US-00003 TABLE 3 Resin or Mixture Temperature Product Example
of Resins Nano-clay (.degree. C.) name 8 MY-0510 Cloisite 25A 25
MEPOXY25A 9 MY-0510 Cloisite Na 25 MEPOXYNa 10 MY-0510 Nanofil 32
25 MEPOXY32 11 MY-0510 Montmo- 25 MEPOXYK10 rillonite K10 12
MY-20CC- Cloisite 25A 25 MEPPU25A 80EP 13 MY-20CC- Cloisite Na 25
MEPPUNa 80EP 14 MY-20CC- Nanofil 32 25 MEPPU32 80EP 15 MY-20CC-
Montmo- 25 MEPPUK10 80EP rillonite K10
Examples for Non-Isocyanate-Based Polyurethanes and
Polyurethane/Epoxy Hybrid Nanocomposite Formulations
Examples 16-18
Preparation of Reference Formulations
[0075] A series of typical reference formulations representing
non-isocyanate-based polyurethane (referred to hereafter as "RPU",
standing for Reference Polyurethane) (Example 16), and
polyurethane-epoxy hybrids (referred to hereafter as "RPUH1" and
"RPUH2" standing for Reference Polyurethane Hybrid 1 and 2) were
prepared (Examples 17 and 18); such formulations did not contain
nano-clays. Table 4 summarizes the composition and the product
names assigned to the reference formulations.
TABLE-US-00004 TABLE 4 Example 16 17 18 RPU RPUH1 RPUH2 Resins and
Hardeners Weight (g) L-803 100 MY-20CC-80EP 100 100 DETA 16.2 TEPA
35.4 14 Ethacure-100 35
Procedure:
[0076] Reference formulations RPU, RPUH and RPUH2 were prepared as
follows:
1.sup.st step: Addition of all the components. 2.sup.nd step:
Thorough mixing.
[0077] The aforementioned reference compositions were cured as
follows yielding different hybrid materials:
RPU:
[0078] Room temperature/1 day (RPU-1) Room temperature/4 days
(RPU-4) (sample only for comparative FT-IR studies) Room
temperature/8 days (RPU-8) Room temperature 1 day and subsequently
at 60.degree. C./4 h (RPU-1-60-4)
RPUH1:
[0079] Room temperature/1 day (RPUH1-1) Room temperature/4 days
(RPUH1-4) Room temperature/1 day and subsequently at 60.degree.
C./4 h (RPUH1-1-60-4) Room temperature/1 day and subsequently at
160.degree. C./4 h (RPUH1-1-160-4)
RPUH2:
[0080] Room temperature/1 day and subsequently at 120.degree. C./4
h (RPUH2-1-120-4)
[0081] The gel times (Micheler test) and isothermal water uptake
measurements of the cured reference resin formulations RPU, RPUH1
and RPUH2 over the course of 60 days of are presented in Table
5.
TABLE-US-00005 TABLE 5 Cured Reference Samples Gel time (min) Water
Uptake (%) RPU 155 25.90 RPUH1 30 11.37 RPUH2 90 0.88
[0082] Water uptake is a reliable measure for determining moisture
(water) permeability of a polymer. The higher the water uptake, the
higher is the affinity of the polymeric matrix to water molecules
and consequently the higher the moisture permeability of this
particular polymer.
[0083] The following Table 6 summarises some of the properties of
the reference compositions.
TABLE-US-00006 TABLE 6 Young's Storage Lap Cured Modulus Shear
Deformation Reference T.sub.g @ 30.degree. C. Strength at maximum
Samples Example (.degree. C.) (MPa) (MPa) load (mm) RPU-1 16
-25.sup.a n.d. 0.74 1.34 RPU-8 16 -20.sup.a n.d. 1.00 0.58
RPU-1-60-4 17 -19.sup.a n.d. 1.04 0.45 RPUH1-1 17 69.sup.b 1024
2.63 0.13 RPUH1-4 17 71.sup.b 1097 3.76 0.15 RPUH1-1-60-4 17
99.sup.b 1014 3.75 0.17 RPUH1-1-160-4 17 113.sup.b 1497 n.d. n.d.
RPUH2-1-120-4 18 147.sup.b 920 n.d. n.d. .sup.aDetermined by DSC,
.sup.bDetermined by DMA
Examples 19-21
[0084] Nanoparticle-containing non-isocyanate-based polyurethane-
("NPU", Example 19) and Nanoparticle-containing hybrid
polyurethane-epoxy nanocomposite polymer compositions (NPUH1 and
NPUH2, Examples 20 and 21, respectively) according to the present
invention were prepared according to the formulation in Table
7.
TABLE-US-00007 TABLE 7 Example 19 20 21 NPU NPUH1 NPUH2 Resins and
Hardeners Weight (g) D4408 (L-803 + Cloisite 110 25A-see Table 2)
D4508 (MY-20CC-80EP + 110 110 Cloisite 25A-see Table 2) DETA 16.2
TEPA 35.2 14 Ethacure-100 35
Procedure:
[0085] Formulations NPU, NPUH1 and NPUH2 were prepared as follows:
1.sup.st step: Addition of all the components. 2.sup.nd step:
Thorough mixing.
[0086] The aforementioned compositions were cured as follows
yielding different nanocomposite materials:
NPU:
[0087] Room temperature/1 day (NPU-1) Room temperature/4 days
(NPU-4) Room temperature/1 day and subsequently at 60.degree. C./4
h (NPU-1-60-4)
NPUH1:
[0088] Room temperature/1 day (NPUH1-1) Room temperature/4 days
(NPUH1-4) Room temperature/1 day and subsequently at 60.degree.
C./4 h (NPUH1-1-60-4) Room temperature/1 day and subsequently at
160.degree. C./4 h (NPUH1-1-160-4)
NPUH2:
[0089] Room temperature/1 day and subsequently at 120.degree. C./4
h (NPUH2-1-120-4)
[0090] The gel times (Micheler test) and isothermal water uptake
measurements over 60 days of the cured formulations NPU, NPUH1 and
NPUH2, are presented in Table 8.
TABLE-US-00008 TABLE 8 Cured Nanocomposite Samples Gel time (min)
Water Uptake (%) NPU 135 20.56 NPUH1 18 1.77 NPUH2 60 0.75
[0091] By comparing Tables 5 and 8, it can be seen that the
presence of nano-clays in NPU, NPUH1, and NPUH2 reduces gel time
and reduces water uptake as compared to the corresponding reference
samples that do not contain nano-particles, RPU, RPUH1, and
RPUH2;
[0092] The following Table 9 summarizes some of the properties of
the nano-particle compositions of the present invention.
TABLE-US-00009 TABLE 9 Young's Storage Cured Modulus @ Lap Shear
Deformation at Nanocomposite T 30.degree. C. Strength maximum load
Samples (.degree. C.) (MPa) (MPa) (mm) NPU-1 -10.sup.a n.d. 1.37
0.96 NPU-4 -9.sup.a n.d. 1.51 0.51 NPU-1-60-4 -9.sup.a n.d. 1.78
0.43 NPUH1-1 69.sup.b 912 2.68 0.13 NPUH1-4 74.sup.b 1190 3.46 0.14
NPUH1-1-60-4 112.sup.b 1013 5.19 0.23 NPUH1-1-160-4 154.sup.b 1803
n.d. n.d. NPUH2-1-120-4 143.sup.b 1646 n.d. n.d. .sup.aDetermined
by DSC, .sup.bDetermined by DMA indicates data missing or illegible
when filed
[0093] By comparing the results in Table 9 for the cured resins
containing nanoparticles with the results in Table 6 for the
reference cured resins (RPU) that do not contain nanoparticles, it
can be seen that the resins containing nanoparticles generally have
better physical properties. The presence of the nano-clay decreased
the gel time by 13%, as compared to the reference RPU formulation
that contained no nano-clay and also the use of nano-clays: [0094]
increases the glass transition temperature (T.sub.g), [0095]
improves the lap shear strength, which is directly related to
adhesion properties, and [0096] reduces deformation. Examples
showing the Catalytic Activity of Nanoclays on Cyclocarbonate
Resins and Cyclocarbonate-Epoxy Resins
Example 22
Preparation of Reference Epoxy Formulation (RPE)
[0097] 5 g of MY-0510 were hand-mixed for 2 min with 1.33 g of TEPA
at ambient temperature. The gel time of this formulation was 106
min.
Examples 23-34
[0098] Non-isocyanate-based polyurethane- and hybrid
polyurethane-epoxy nanocomposite polymer compositions according to
the present invention were prepared according to the formulations
presented in Table 10. The gel times of all formulations was
measured after 2 minutes of hand mixing of their ingredients. For
comparative reasons, the data of Examples 20 (NPUH1, in Table 7)
and 22 (RPE) were also included as Example 31 and RPE in Table
10.
TABLE-US-00010 TABLE 10 Components of polymeric compositions (with
Example Number amounts indicated in grams) RPE 23 24 25 26 27 28 29
30 31 32 33 34 MY-0510 5.00 5.00 5.00 5.00 Example 8 (MY-0510 +
Cloisite 25A) 5.50 Example 9 (MY-0510 + Cloisite Na) 5.50 Example
11 (MY-0510 + Montmorillonite K10) 5.50 Example 7 (MY-0510 +
Nanofil 32) 5.50 Example 6 (MY-0510 + Cloisite 25A) 5.50 Example 1
(MY-20CC-80EP) 4.00 Example 12 (MY-20CC-80EP + Cloisite 25A) 4.44
Example 13 (MY-20CC-80EP + Cloisite Na) 4.44 Example 4
(MY-20CC-80EP + Cloisite 25A) 4.44 TEPA 1.33 1.33 1.33 1.33 1.33
1.33 1.42 1.42 1.42 1.42 1.33 1.33 1.33 Arquad-DMHTB-75 0.10 0.20
Benzyltrimethyl ammonium chloride 0.10 Gel time (min) 106 85 93 93
75 88 30 32 32 18 95 95 95 % Decrease in gel time of the RPE n.a.
20 12 12 29 17 72 70 70 83 10 10 10
[0099] As can be seen from Table 10, the introduction of nano-clays
into both conventional cyclocarbonate-based polyurethane
compositions and cyclocarbonate/epoxy-based compositions (Examples
23-27 and 29-31) resulted in substantially decreased gel time (even
up to 83% upon compared to RPE) as compared to those compositions
without the nanoclay (Examples RPE, 28 and 32-34).
[0100] From the data presented in Table 10, it is clear that curing
can be accelerated by 12-20% by introducing nanoclays (compare RPE
with Examples 23-27), showing that the nano-clays have a catalytic
effect.
[0101] In T. Lan, P. D. Kaviratna, T. J. Pinnavaia, Chem. Mater. 7,
2144-2150, 1995 and Z. Wang, T. J. Pinnavaia, Chem. Mater. 10,
1820-1826, 1998, it has been reported that acidic primary onium
ions when they are ion-exchanged for the inorganic cations of the
parent layered silicates catalyze intergallery epoxide
polymerization process in the presence of an amine curing agent.
However, it can be seen from the results in Table 10 (see Examples
24 and 25) that even natural non-modified nano-clays can catalyze
the reaction of an epoxy resin with an amine as these two
formulations presented lower gel times (12%) than the reference
formulation RPE. Differences in the catalytic activity of various
commercially available nano-clays cannot be excluded. The
formulation of Example 26 presented decreased gel times compared
with the formulations of Examples 23-25 where the organoclays where
simply hand mixed with the curable mixture. In addition, the
Example 23 formulation presented lower gel time than the
compositions of Examples 32-34.
[0102] When epoxides are formulated with cyclocarbonated resins,
the gel time is significantly decreased compared to RPE. More
particularly, the use of a mixture of a cyclocarbonate resin, an
epoxy resin and an amine (calculated to react with both resins)
resulted to a dramatic decrease of the gel time (compare the
results of RPE with that of Example 28 in Table 10).
[0103] Without being bound to any particular theory for the low gel
time of the mixture of cyclocarbonated and epoxy resins and a
nanoclay cured with an amine hardener, as shown in Examples 29 to
31, it is believed that it is brought about as follows: Two main
crosslinking reactions can take place when curing a mixture of
cyclocarbonated and epoxy resins with an amine hardener: a) the
reaction of the carbonyl of the 1,3-dioxolan-2-one ring with the
amine, resulting to a polyurethane group (polyurethane reaction)
and b) the reaction of the epoxide with the amine, resulting in a
polyepoxy (polyepoxy reaction). Thus the presence of cyclocarbonate
and epoxy resins together with amine hardeners leads to the
formation of a copolymer or an interpenetrated network (IPN). It is
believed that, due to its short induction time, the polyurethane
reaction proceeds faster than the epoxy reaction; both reactions
are exothermic and, depending on the reaction mass and the initial
curing temperature, the polyurethane reaction will generally
proceed until a temperature is reached at which the polyepoxy
reaction is triggered, when the temperature will rise more quickly,
thereby further increasing the rate of curing. The natural or
modified nanoclays appear to catalyse not only the reaction of the
carbonyl of the cyclocarbonate (1,3-dioxolan-2-one) ring with the
hardener (e.g. aliphatic amine) but also the reaction of the
epoxide with the hardener (amine), giving a reduced gel time,
exemplified particularly of Example 31, where the gel time (18 min)
was 83% less of the gel time of RPE (106 min).
[0104] Generally, the nanofillers need not be dispersed at a
nanoscale in order for the catalysis to be effective but generally
some sort of dispersion is preferable in order to produce the full
benefit of the improved physical properties of the present
invention.
Example 35
[0105] FIG. 1 is the FT-IR spectra of: [0106] 1. L-803, [0107] 2.
RPU-1 (which is L-803+DETA, see Example 16 in Table 4 after 1 day
cure) and [0108] 3. NPU-1 (which is L-803+Cloisite 25A+DETA, see
Example 19 in Table 7, after 1 day cure) FIG. 2 is the FT-IR
spectra of: [0109] 1. RPU-4 (which is L-803+DETA, see Example 16 in
Table 4 after 4 days cure) and [0110] 2. NPU-4 (which is
L-803+Cloisite 25A+DETA, see Example 19 in Table 7, after 4 days
cure)
[0111] FIGS. 1 and 2 provide clear evidence of the substantially
decreased reaction time when the compositions contain nano-clays.
The absorption at 1795 cm.sup.-1 attributed to the carbonyl of the
cyclocarbonate groups (1,3-dioxolan-2-one rings) (see FT-IR
spectrum of L-803 resin), is almost three times less in the FT-IR
spectrum of NPU-1 as compared to that of the reference polyurethane
RPU-1. Moreover, after 4 days curing at ambient temperature NPU-4
does not present any absorption at 1795 cm.sup.-1 (indicative of
complete reaction of the cyclocarbonate groups with the amine
crosslinker) whilst RPU-4 still presents some unreacted
cyclocarbonate groups. The reference polyurethane RPU is fully
crosslinked (no absorption at 1795 cm.sup.-1) after 7-8 days at
ambient temperature.
Example 36
[0112] Isothermal water uptake is a measure for addressing the
moisture permeability of polymers; the isothermal water uptake of
compositions RPU and NPU; RPUH1 and NPUH1; and RPUH2 and NPUH2 was
measured over time and the results are shown in FIGS. 3 to 5.
Surprisingly, in all cases, the formulations containing the
nano-clays have substantially lower water permeability by approx.
14-85% w/w which is directly attributed to the organoclays; it is
believed that the introduction of the organoclays into the
polymeric network results in the formation of an internal barrier
hindering the penetration of the water molecules into the matrix
and decreases the capability of the polar atoms/groups (oxygens,
hydroxyls, imino, urethane --NH, etc.) present in the matrix to
attract water molecules via the formation of hydrogen bonds. After
isothermal moisture absorption for 1440 h (60 days), NPUH2
presented the lowest water permeability, only 0.75% and the RPU the
highest (25.90%).
* * * * *